For all of our advances in understanding the biology of a cancer cell, the cornerstone of therapy for advanced cancers remains drugs that are non-specifically cytotoxic. The challenge is to identify key molecular targets that underlie the malignant behavior of a cancer cell, and to target these directly. Since the phenotype of a cancer cell is largely driven by the pattern of genes expressed in the cell, much attention has focused on the inappropriate activation of transcription factors that regulate genes controlling proliferation, survival, self-renewal, and invasion. Two such oncogenic transcription factors are STAT3 and NF-kB. Through our research on developing targeted inhibitors of these proteins we have found that when STAT3 function is blocked by small molecule inhibitors, the activity of NF-kB often increases. This increase in NF-kB activity attenuates the effect of STAT3 inhibitors on cancer cells and raises a number of important mechanistic questions about the molecular and functional interaction between these proteins. To exploit these findings for cancer therapy, we set out to develop compounds that could simultaneously block the effects of STAT3 and NF-kB. Through a high throughput cell-based screen of approximately 200,000 compounds, and a related synthetic chemistry effort, we have identified two compounds that specifically block both of these transcription factors. These dual STAT3/ NF-kB inhibitors may represent a unique strategy for cancer therapy. We now propose to build on these observations to further understand the interaction between STAT3 and NF-kB in cancer cells, and to elucidate the potential for these dual inhibitors in the treatment of cancer. Focusing on breast cancer and multiple myeloma, tumors that frequently display co-activation of STAT3 and NF-kB, three aims will be pursued: (1) To discern the relationship between STAT3 inhibition and NF-kB activation in cancer cells. (2) To elucidate the molecular effects of dual STAT3/ NF-kB inhibitors in cancer cells. (3) To assess the effects of dual STAT3/ NF-kB inhibitors on the biology of cancer cells in cell culture and animal models. There is a great need for innovative treatments for advanced cancer that are targeted to the molecular defects driving the malignant behavior of these cells. The ultimate goal of this work is to elucidate the role that STAT3 and NF-kB are playing in cancer cells, and to determine the potential of simultaneously targeting both proteins as a form of molecular therapy for patients with cancer. PUBLIC HEALTH RELEVANCE: We have found that two key proteins, STAT3 and NF-kB, interact to drive the malignant behavior of a cancer cell, and we therefore developed molecules that can specifically inhibit these proteins. We now propose to determine how effective these chemicals will be as potential anti-cancer drugs. The focused goal of this work is to develop more effective and less toxic treatments for patients with cancer.